Field of the Invention
The present invention relates to a switch.
Description of the Related Art
For example, Japanese Patent Laid-Open No. 2012-074310 discloses an inhibitor switch that is mounted on a vehicular automatic transmission to detect a selection range of a shift lever.
FIG. 7A and FIG. 7B are diagrams for explaining an inhibitor switch 10 according to the conventional switch that is represented by the inhibitor switch disclosed in Japanese Patent Laid-Open No. 2012-074310, wherein FIG. 7A is an exploded perspective view showing the inhibitor switch 10, and FIG. 7B is a cross section showing a movable board 5, taken along a plane A in FIG. 7A and is a diagram for explaining an arrangement of movable contact points 7 in the movable board 5.
A body case 4 of the inhibitor switch 10 is formed by coupling a cover 3 to a peripheral wall 24 that surrounds an area of a pole board 2 where fixed contact points 8 are disposed, and the movable board 5 provided with the movable contact points 7 is provided inside the body case 4 to be rotatable around an axis line X.
The movable board 5 includes a cylindrical shaft portion 51 and a contact point holding portion 52 extending in a radial direction (radial direction of the axis line X) from the shaft portion 51, and each of the movable contact points 7 is accommodated in an accommodation hole 53 formed in the contact point holding portion 52 together with a spring Sp (refer to FIG. 7B).
Each of the movable contact points 7 projects downward to the side of the pole board 2 from the accommodation hole 53 by an urging force acting from the spring Sp, and is configured to make pressure-contact with the fixed contact point 8 exposed on an upper surface of the pole board 2 in a state where the movable board 5 is assembled in the body case 4.
An arm (member in the side of a shift lever) rotating in association with an operation of the shift lever is coupled to the shaft portion 51 of the movable board 5. When the shift lever is operated, the contact point holding portion 52 extending in the radial direction from the shaft portion 51 rotates around the axis line X in association with the operation of the shift lever. Thereby, the movable contact point 7 having made pressure-contact with the fixed contact point 8 moves in a circumferential direction around the axis line X.
In the inhibitor switch 10, when the movable board 5 rotates by the operation of the shift lever, the movable contact point 7 moves while sliding on the fixed contact point 8, thus causing a position of the movable contact point 7 around the axis line X to change.
Therefore, grease is applied inside the peripheral wall 24 that surrounds the area of the pole board 2 in which the fixed contact points 8 are provided, for reducing a sliding resistance to be generated at the time the movable contact point 7 slides on the fixed contact point 8. Accordingly, at the rotating of the movable board 5, the movable contact point 7 slides while scratching and separating the grease that has covered the upper surface of the fixed contact point 8, thereby retaining the contacting state between the movable contact point 7 and the fixed contact point 8.
However, since fluidity of the grease is generally lowered under low-temperature environments, there are some cases where the scratching and separating of the grease by the movable contact point 7 becomes insufficient.
In that case, there are some cases where the movable contact point 7 moving in association with rotation of the movable board 5 gets on the grease, which generates a non-contacting state between the movable contact point 7 and the fixed contact point 8 that should originally make contact with each other or a chattering phenomenon that the movable contact point 7 and the fixed contact point 8 are repeatedly connected/disconnected in a short cycle.
Therefore, it is required to cause the movable contact point 7 to certainly make contact with the fixed contact point 8 even in a case where the fluidity of the grease is low.